The present invention relates to a continuously operating preliminary or finishing press for the manufacture of particle boards such as chip or fiber boards or the like with two horizontal and parallel endless plate belts arranged one above the other and revolving around polygonal drums. Each endless belt consists of plates hinged to one another only in the area of the side surfaces thereof, i.e., only along their outer lateral edges. The edges of the plates extending transversely to the direction of movement of each endless plate belt are provided with essentially rectangular recesses and projections. See German Pat. No. 2,107,845.
The recesses and projections, provided at the individual plates of the endless plate belts exhibit, in the previously mentioned known presses, rectangular shapes, and adjacent plates are in this area pivotably connected one to the other through bolts, the lengths of which correspond to the plate widths. In order to keep the cross-sections of the bolts as small as possible, the number of recesses and projections is relatively high. The pressure forces generated therefore, are uniformly transmitted by each of the bolts. This solution is disadvantageous because the front edges of the projections of the plates in the area of impact spot may be deformed, this being due to the large number of recesses and projections and the necessary clearance of the bolts which increases with longer operating time. Even though danger of this deformation is not so great when the endless plate belts lie on pressure surfaces with relatively large lengths, this danger to deform the edges of the plates lying transversely to the direction of movement of the plate belts is particularly significant when the adjacent runs of the two endless plate belts, arranged one above the other, are acted on at least partly by driveable press-on drums or rollers.
In order to avoid this disadvantage, it was suggested in unpublished German unexamined published application No. 2,320,178 (U.S. Pat. No. 3,883,284) to shape the recesses and projections trapezoidally to triangularly, and to connect adjacent plates with each other by guide elements supported only in the zone of the lateral surfaces of the plates approximately the depth of the recesses of adjacent plates. In addition, each projection is equipped at its free end and each recess at its base with a rabbet and a flange. When viewed in the direction of the corresponding endless plate belts, each plate engages the subsequent plate in the entering area of the press in such a way that the flanges at the free end of the projections of each plate move into the open rabbets at the bases of the recesses of the preceeding plate. This solution has proven itself because the bending forces taken up by the projection of the plates are absorbed more easily and further because the press-on drums or rollers in the area of the impact points of adjacent plates are always in good contact. This solution is very suitable for the endless plate belts of finishing presses. This solution is not suitable for preliminary presses because the relatively long projections dig too deeply into the particle cake or fleece. If a particle cake is, however, already precompressed, only an additional compression must follow. In these situations, the relatively long projections do not have a disadvantageous effect, even though a certain pressure must be exerted on a precompressed particle cake to extend the time for hardening because the projections already lie in a plane.